Add open todo count badge to sidebar menu

Shows number of non-done todos (todo + in_progress) next to the
Todos nav item. Hides when count is zero.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/components/layout/Sidebar.svelte

@@ -4,7 +4,7 @@
 	interface Props {
 		open: boolean;
 		onToggle: () => void;
-		counts: { devices: number; components: number; needsRepair: number };
+		counts: { devices: number; components: number; needsRepair: number; openTodos: number };
 	}
 
 	let { open, onToggle, counts }: Props = $props();
@@ -40,6 +40,7 @@
 		{
 			href: '/todos',
 			label: 'Todos',
+			badge: counts.openTodos || undefined,
 			icon: 'M9 12l2 2 4-4m6 2a9 9 0 11-18 0 9 9 0 0118 0z'
 		},
 		{